1 /*
2 * Copyright (C) 2020 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 // This example demonstrates in-process tracing with Perfetto.
18
19 #include "trace_categories.h"
20
21 #include <chrono>
22 #include <fstream>
23 #include <thread>
24
InitializePerfetto()25 void InitializePerfetto() {
26 perfetto::TracingInitArgs args;
27 // The backends determine where trace events are recorded. For this example we
28 // are going to use the in-process tracing service, which only includes in-app
29 // events.
30 args.backends = perfetto::kInProcessBackend;
31
32 perfetto::Tracing::Initialize(args);
33 perfetto::TrackEvent::Register();
34 }
35
StartTracing()36 std::unique_ptr<perfetto::TracingSession> StartTracing() {
37 // The trace config defines which types of data sources are enabled for
38 // recording. In this example we just need the "track_event" data source,
39 // which corresponds to the TRACE_EVENT trace points.
40 perfetto::TraceConfig cfg;
41 cfg.add_buffers()->set_size_kb(1024);
42 auto* ds_cfg = cfg.add_data_sources()->mutable_config();
43 ds_cfg->set_name("track_event");
44
45 auto tracing_session = perfetto::Tracing::NewTrace();
46 tracing_session->Setup(cfg);
47 tracing_session->StartBlocking();
48 return tracing_session;
49 }
50
StopTracing(std::unique_ptr<perfetto::TracingSession> tracing_session)51 void StopTracing(std::unique_ptr<perfetto::TracingSession> tracing_session) {
52 // Make sure the last event is closed for this example.
53 perfetto::TrackEvent::Flush();
54
55 // Stop tracing and read the trace data.
56 tracing_session->StopBlocking();
57 std::vector<char> trace_data(tracing_session->ReadTraceBlocking());
58
59 // Write the result into a file.
60 // Note: To save memory with longer traces, you can tell Perfetto to write
61 // directly into a file by passing a file descriptor into Setup() above.
62 std::ofstream output;
63 output.open("example.pftrace", std::ios::out | std::ios::binary);
64 output.write(&trace_data[0], trace_data.size());
65 output.close();
66 }
67
DrawPlayer(int player_number)68 void DrawPlayer(int player_number) {
69 TRACE_EVENT("rendering", "DrawPlayer", "player_number", player_number);
70 // Sleep to simulate a long computation.
71 std::this_thread::sleep_for(std::chrono::milliseconds(500));
72 }
73
DrawGame()74 void DrawGame() {
75 // This is an example of an unscoped slice, which begins and ends at specific
76 // points (instead of at the end of the current block scope).
77 TRACE_EVENT_BEGIN("rendering", "DrawGame");
78 DrawPlayer(1);
79 DrawPlayer(2);
80 TRACE_EVENT_END("rendering");
81
82 // Record the rendering framerate as a counter sample.
83 TRACE_COUNTER("rendering", "Framerate", 120);
84 }
85
main(int,const char **)86 int main(int, const char**) {
87 InitializePerfetto();
88 auto tracing_session = StartTracing();
89
90 // Give a custom name for the traced process.
91 perfetto::ProcessTrack process_track = perfetto::ProcessTrack::Current();
92 perfetto::protos::gen::TrackDescriptor desc = process_track.Serialize();
93 desc.mutable_process()->set_process_name("Example");
94 perfetto::TrackEvent::SetTrackDescriptor(process_track, desc);
95
96 // Simulate some work that emits trace events.
97 DrawGame();
98
99 StopTracing(std::move(tracing_session));
100 return 0;
101 }
102